1. Field of the Invention
The present invention relates to a manufacturing method and apparatus of a ceramic matrix composite member and carbon-based composite material which can accurately be provided with machining bases (axial center and reference surface) during machining.
2. Description of the Related Art
In order to raise the performance of a rocket engine using NTO/N2H4, NTO/MMH, and the like as impelling agents, heat-resistant temperature of a combustor (thrust chamber) is requested to be raised. For this purpose, a coated niobium alloy having a heat-resistant temperature of about 1500xc2x0 C. has heretofore been used as a chamber material for many rocket engines. However, this material is disadvantageously heavy because of its high density, low in high-temperature strength, and has a short coating life.
On the other hand, since ceramic is high in heat resisting properties but disadvantageously brittle, a ceramic matrix composite member (hereinafter abbreviated as CMC) has been developed by reinforcing the ceramic with ceramic fiber. Specifically, a ceramic matrix composite member (CMC) comprises ceramic fiber and ceramic matrix. Additionally, in general the CMC is indicated as ceramic fiber/ceramic matrix by its material (e.g., when both are formed of SiC, SiC/SiC is indicated).
Since CMC is light-weight and high in high-temperature strength, it is a remarkably prospective material for the combustor (thrust chamber) of the rocket engine, further a fuel piping in a high-temperature section, a turbine vane of a jet engine, a combustor, an after-burner component, and the like.
However, the conventional CMC cannot hold its hermetic properties and is disadvantageously low in resistance to thermal shock. Specifically, for the conventional CMC, after a predetermined shape is formed of ceramic fibers, a matrix is formed in a gap between the fibers in so-called chemical vapor infiltration (CVI) treatment. However, a problem is that it takes an impractically long time (e.g., one year or more) to completely fill the gap between the fibers by the CVI. Moreover, in a high-temperature test or the like of the conventional CMC formed as described above, when a severe thermal shock (e.g., temperature difference of 900xc2x0 C. or more) acts, the strength is drastically lowered, and the CMC can hardly be reused.
Therefore, the conventional ceramic matrix composite member (CMC) cannot substantially be used in the combustor (thrust chamber), the fuel piping or another component requiring the hermetic properties and resistance to thermal shock.
In order to solve the aforementioned problem, the present inventor et al. have created and filed a patent application, xe2x80x9cCeramic-based Composite Member and its Manufacturing Methodxe2x80x9d (Japanese Patent Application No. 19416/1999, not laid yet). The Ceramic-based Composite Member can largely enhance the hermetic properties and thermal shock resistance and which can be for practical use in the thrust chamber, and the like. In the invention, as schematically shown in FIG. 1, after subjecting the surface of a shaped fabric to CVI treatment to form an SiC matrix layer, PIP treatment is performed to infiltrate and calcine a gap of the matrix layer with an organic silicon polymer as a base.
In a manufacture process shown in FIG. 1, from a braiding process (1) to a CVI process (3), a jig or mandrel, for example, of carbon or the like is used to form a fabric 1 in a periphery and subsequently, the CVI treatment is performed. Since matrix is formed in the gap of the fabric 1 by the CVI treatment and a shape is held, in this stage, the mandrel is detached, and subsequent PIP treatment (4) and machining (5) are performed in a conventional art. Additionally, in the braiding process, as schematically shown in FIG. 2, for example, braid weave is used in which a braided thread is alternately and obliquely woven into a middle thread.
However, a ceramic matrix composite member 2 subjected to the CVI treatment and PIP treatment after the braiding process (e.g., braid weave) is large in surface concave/convex, and there is a problem that a machining basis cannot be established. Specifically, as schematically shown in FIG. 3, since the concave/convex of the surface of a semi-finished product (ceramic matrix composite member 2) is large, a machining reference point/surface cannot precisely be defined, and for example, by determining an axial center in such a manner that deflection of rotation around Zxe2x80x94Z axis of FIG. 3 is minimized, and further determining, for example, a minimum diameter position in this situation, the position is set as a positioning basis of an axial direction. Therefore, in such method, it is impossible to accurately determine the axial center or the reference surface of the axial direction, and as a result, a defect of a cut place of the axial direction, non-uniformity of a product plate thickness by one-side contact machining (cut of reinforced fiber) and other machining precision defects are caused.
Moreover, in order to solve the problem, it is preferable to attach the mandrel even during machining, but in this case, the product adheres to the mandrel by the matrix in the CVI or PIP treatment, it becomes difficult or impossible to detach the product, and there is a problem that product breakage rate increases and product yields are remarkably lowered.
The present invention has been developed to solve the problem. Specifically, an object of the present invention is to provide a manufacturing method and apparatus of a fiber reinforced composite member in which machining bases (axial center and reference surface) during machining can accurately be provided without possibility of adhesion to a mandrel and resulting breakage, so that machining precision and yield of a final product can largely be improved.
According to the present invention, there is provided a manufacturing method of a fiber reinforced composite member comprising steps of: forming a fabric on the surface of a mandrel; infiltrating the formed fabric with matrix; and leaving a part of the mandrel which is integral with the fabric and removing the mandrel.
According to a preferred embodiment, the left part of the mandrel which is integral with the fabric is used as a reference surface to perform machining. Moreover, the fabric is formed to be longer than a product dimension.
According to the method of the present invention, since a part of the mandrel is left as integral with the fabric and the mandrel is detached, a product portion failing to contact the left mandrel can sufficiently be infiltrated with the matrix and formed similarly as a conventional art. Moreover, since a part of the mandrel is left in a semi-finished product (fiber reinforced composite member) after matrix infiltration treatment, by using the part of the mandrel as the machining bases (axial center and reference surface) during machining, an axial direction position and axial center determined on the mandrel can be held constant. Therefore, by setting the reference surface beforehand to be a smooth surface, even with a large concave/convex of the surface of the semi-finished product, the machining basis can accurately be provided, non-uniformity of a machined plate thickness can be eliminated, shape precision is improved, and further strength deterioration by cutting of fiber can be inhibited.
Moreover, according to the present invention, there is provided a manufacturing apparatus of a fiber reinforced composite member for forming a fabric on the surface of a mandrel, and infiltrating the formed fabric with matrix, wherein the mandrel is formed to be longer than a product dimension of a fiber reinforced composite member.
According to the preferred embodiment of the present invention, a portion of the mandrel protruding from the product dimension of the fiber reinforced composite member has a portion whose diameter increases toward an end, and the diameter increasing portion can be separated into an annular portion having a diameter larger than an outer diameter of a product dimension end portion and a remaining portion in a constitution.
By the constitution, the annular portion having the diameter larger than the outer diameter of the product dimension end portion is left as integral with the fabric, and the remaining portion can be removed.
Moreover, it is preferable to form a groove or a protrusion interlocking with the fabric on the surface of the annular portion in such a manner that when the part of the mandrel forming the product portion is removed, the mandrel left as integral with the fabric fails to move on the fabric. By this constitution, connection/integration of the annular portion with the fiber reinforced composite member is reinforced, and displacement of the annular portion during removing of the mandrel can be prevented.
Other objects and advantageous characteristics of the present invention will be apparent from the following description with reference to the accompanying drawings.